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Need help identifying microorganisms from tropical fish - (Nov/17/2008 )

I just lost a tropical fish (flame tetra) to perforated stomach. It is unclear why the fish developed a perforated stomach. It shares a tank with two dozen other fish who are in good health. It developed dark spots on both sides of its body behind the gills three days ago, and acted fairly normal. Yesterday the dark spots expanded, it developed swelling on its lower right abdomen, then I saw it expel thick hard dark fecal material from a perforation in its abdomen in front of the pelvic fins and directly under its stomach (nowhere near its vent). The dark spots shrank. Fish acted normal if grouchy toward the other fish, but I euthanized it this morning because no fish could survive all that perforation. I

I autopsied the fish. On the side that I did not cut open the dark spots were actually created by holes in the muscle under teh skin, the size, shape and location of the dark spots. The skin was not broken.

The liver was brown, which my books say is normal only in vegetarian fish and these are omnivores, and it was smaller than the photos and diagrams online say it ought to be. Teh stomach was shredded and that's about all one can say about it. Part of the intestine may have been larger than normal but nothing was in it. I could not tell what caused the blockage.

Then I made microscopic slides, one from the liver and three from a general mash of the intestines and other organs in the area. (I don't have teh skill to sort them out.). Most are at 400X; a few are at 100X, and the later photos are using methylene blue. Some photos were cleared up in Paint Shop Pro. I can say that the fish does not appear to ahve intestinal worms and has no flagellates, but I cannot tell if there are unicellular pathological organisms present or not. One would expect to see bubbles, globules of fat, blood cells, and signs of secondary infection, and in one place I suspect there are urate crystals. There are long rod shaped things in the liver where I do not think they belong, and they're too big for bacillae. Some of the globs appear to have internal structures, and in some cases teh structures look organized and uniform between different globs. Some round globs have concentric organzation.

Does anyone see anything pathological in these photos? I need to know whether to treat my other fish.

Also, does anyone know wehre else I might ask. On the fish lists and forums all they've been able to think about for three days is my water chemistry (which was tested thoroughly and is perfectly normal, and hardly selectively blocked the intestines, damaged the muscles or liver, or perforated the stomach of one fish). On a microscopy list at Yahoo groups, someone wanted to know if my fish could have been poisoned with melamine! No particular reason. It just happened to occur to him.


Dora Smith


Wish I had something more intelligent to say than to check Dieter Untergasser's "Handbook of Fish Diseases," which is pretty good on the "how to" side of necropsying a fish. "Textbook of Fish Health" by Post is also very good, but more technical and aquaculture-oriented than for the hobbyist, unlike Untergasser. Sorry not to be of more help!